Patent Document 1 discloses a drive for rotating an upper rotating structure of a hydraulic excavator. The drive includes an electric motor for generating drive force. Further, the drive includes a hydraulic motor coupled to an output shaft of the electric motor. The drive uses the hydraulic motor as a brake for stopping the rotation of the rotating structure, thereby quickly stopping the rotating structure having a large inertial force (see paragraphs [0007] and [0010] of Patent Document 1). The drive uses the hydraulic motor to compensate for decrease in torque when the electric motor rotates in a high speed rotation range (see paragraph [0025] of Patent Document 1).    [Patent Document 1] Japanese Patent Publication No. 2005-344431